Method for accessing cell, and base station

ABSTRACT

Method for accessing cell and base station are provided. The method includes: transmitting system information indicating whether the cell supports connection resume function to a UE; after receiving an RRC connection resume request from the UE, acquiring a resume identification of the UE from the RRC connection resume request; looking up context information of the UE based on the resume identification, and transmitting an RRC connection resume acknowledgement message to the UE after finding the context information; after determining an MME supports connection resume function, transmitting a context information activation request including identification information of the UE to the MME; receiving a context information activation acknowledgement message from the MME, which is transmitted after the MME finds the context information of the UE according to the identification information; and transmitting a notification message indicating that a bearer is resumed to the UE. Failure in connection resume procedure is avoided.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Chinese patent applicationNo. 201610018109.7, filed on Jan. 12, 2016, and entitled “METHOD FORACCESSING CELL AND BASE STATION”, and the entire disclosure of which isincorporated herein by reference.

TECHNICAL FIELD

The present disclosure generally relates to wireless communicationfield, and more particularly, to a method for accessing a cell, and abase station.

BACKGROUND

In a Long-Term Evolution (LTE) system, when a User Equipment (UE) isconnected in, a base station allocates necessary parameters for the UE,such as security algorithm, configuration parameters for a medium accesscontrol layer (Layer 2), configuration parameters for a physical layer(Layer 1), and configuration parameters for a radio link control layer(Layer 3), for example, radio link failure parameters. Regarding anestablished bearer, the base station should be aware of informationabout a channel between the bearer and a core network (i.e., a GTPtunnel). All the parameters mentioned above are called UE contextinformation.

In 3GPP Release 13, for some low-cost UE, established services aregenerally services with time delay tolerant. To reduce signalingoverhead for accessing a network, a Radio Resource Control (RRC) suspendor resume mechanism is introduced. In this mechanism, a UE when turningfrom a connected state to an idle state should save context informationconfigured for accessing a network currently, a base station saves thecontext information of the UE which includes configuration parametersfor an access layer of the UE, and further Mobility Management Entity(MME) in a core network also saves the context information of the UEwhich includes configuration parameters for a non-access layer of theUE, GTP tunnel and so on.

When the UE is indicated to enter the idle state, the base station sendsa certain identification to the UE, called Resume ID. When the UE isaccessed to the network again, the UE initiates a connection resumeprocedure to indicate its Resume ID to the base station. The basestation identifies the UE according to the Resume ID, and resumes aservice tunnel (including GTP tunnel at interface S1 and data radiobearer at a corresponding air interface) established for the UE formerlyusing the saved context information of the UE. In this way, the UE canperform data transmission through the service tunnel again. In the aboveprocedure, there is no need to configure radio resources repeatedly,which greatly reduces signaling overhead.

However, the UE cannot determine whether the selected base stationsupports the resume procedure, thus, the existing resume mechanism maycause failure in the connection resume procedure.

SUMMARY

In embodiments of the present disclosure, failure in a connection resumeprocedure may be avoided.

In an embodiment of the present disclosure, a method for accessing acell is provided, including: transmitting system information to a UE,wherein the system information includes information indicating whetherthe cell supports a connection resume function; after receiving an RRCconnection resume request from the UE, acquiring a resume identificationof the UE from the RRC connection resume request; looking up contextinformation of the UE based on the resume identification, andtransmitting an RRC connection resume acknowledgement message to the UEafter the context information is found; after determining that an MMEsupports the connection resume function, transmitting a contextinformation activation request to the MME, wherein the contextinformation activation request includes identification information ofthe UE; receiving a context information activation acknowledgementmessage from the MME, wherein the context information activationacknowledgement message is transmitted after the MME finds the contextinformation of the UE according to the identification information of theUE; and transmitting a notification message to the UE, wherein thenotification message includes information indicating that a bearer isresumed.

Optionally, determining the MME to support the connection resumefunction may include: determining that a message which includesinformation indicating that the MME supports the connection resumefunction is received from the MME.

Optionally, the message which includes information indicating that theMME supports the connection resume function may be one of the followingmessages: S interface setup response message; an MME configurationupdate message; and a deactivation acknowledgement message fed back bythe MME, wherein the deactivation acknowledgement message is generatedafter the MME receives a deactivation message.

Optionally, the system information may include an indication informationelement which is used for indicating whether the cell supports theconnection resume function.

Optionally, the indication information element may be set in a systeminformation block 1.

Optionally, there may be a plurality of indication information elementswhich correspond to different Public Land Mobile Network (PLMN)identifications, respectively.

Optionally, when the UE which has saved the resume identificationperforms cell reselection, if a plurality of cells are detected to havemaximum signal strength values at different frequencies and meet a cellreselection criterion, a cell selected by the UE preferentially is thecell supporting the connection resume function.

In an embodiment of the present disclosure, a based station is provided,including: a first transmitting unit, configured to transmit systeminformation to a UE, wherein the system information includes informationindicating whether the cell supports a connection resume function; anacquiring unit, configured to acquire a resume identification of the UEfrom an RRC connection resume received from the UE; a looking up unit,configured to look up context information of the UE based on the resumeidentification; a second transmitting unit, configured to transmit anRRC connection resume acknowledgement message to the UE after thecontext information is found by the looking up unit; a determining unit,configured to determine that an MME supports the connection resumefunction; a third transmitting unit, configured to transmit a contextinformation activation request to the MME, wherein the contextinformation activation request includes identification information ofthe UE; a receiving unit, configured to receive a context informationactivation acknowledgement message from the MME, wherein the contextinformation activation acknowledgement message is transmitted after theMME finds the context information of the UE according to theidentification information of the UE; and a fourth transmitting unit,configured to transmit a notification message to the UE, wherein thenotification message includes information indicating that a bearer isresumed.

Optionally, the determining unit may be configured to determine that amessage which includes information indicating that the MME supports theconnection resume function is received from the MME.

Optionally, the message which includes information indicating that theMME supports the connection resume function may be one of the followingmessages: S1 interface setup response message; an MME configurationupdate message; and a deactivation acknowledgement message fed back bythe MME, wherein the deactivation acknowledgement message is generatedafter the MME receives a deactivation message.

Embodiments of the present disclosure may provide following advantages.The base station informs the UE which cells support the connectionresume function through the system information, and determines whetherthe MME supports the connection resume function. The UE starts toperform the connection resume procedure after knowing that the cellsupports the connection resume function. The base station transmits thecontext information activation request to the MME to inform the MME toactivate the saved context information, after making sure that the MMEsupports the connection resume function. Therefore, the UE initiates theconnection resume procedure at the cell supporting the connection resumeprocedure, and the base station transmits the context informationactivation request to the MME supporting the connection resume function,which may avoid failure in the connection resume procedure.

Further, the indication information element which is used for indicatingwhether the cell supports the connection resume function is set in thesystem information block 1. The UE only needs to read the systeminformation block 1 to know whether the cell supports the connectionresume function. Namely, there is no need to read other systeminformation blocks in the cell, which may reduce the number of systeminformation blocks to be read by the UE and further reduce powerconsumption of the UE.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a flow chart of a method for accessinga cell according to an embodiment; and

FIG. 2 schematically illustrates a structural diagram of a base stationaccording to an embodiment.

DETAILED DESCRIPTION

In existing techniques, when a UE in a connected state is indicated toenter an idle state, a base station sends a certain identification tothe UE, called Resume ID. Both the UE and a network save contextinformation in the current connected state. When the UE is accessed tothe network again, the UE initiates a connection resume procedure toindicate its Resume ID to the base station. The base station identifiesthe UE according to the Resume ID, and resumes a service tunnel(including GTP tunnel at interface S1 and data radio bearer at acorresponding air interface) established for the UE formerly using thesaved context information of the UE. In this way, the UE can performdata transmission through the service tunnel again. In the aboveprocedure, there is no need to configure radio resources repeatedly,which greatly reduces signaling overhead.

To support the resume mechanism, both the base station and the MME needto save the context information of the UE, and the context informationsaved by the base station is not entirely same as that saved by the MME.When the UE is to access the network again, the UE needs to access acell supporting the resume function, and the base station where the cellis located needs to be connected with the MME supporting the connectionresume function. However, in the existing resume mechanism, the UEdoesn't know whether the accessed cell supports the connection resumefunction, and the base station doesn't know whether the connected MMEsupports the connection resume function as well. Therefore, wheninitiating a connection resume procedure, the UE may probably initiatethe procedure to a cell that does not support the connection resumefunction, which may cause failure in the connection resume procedure.Accordingly, the base station may not execute the connection resumeprocedure successfully as it doesn't know whether the connected MMEsupports the connection resume function.

In embodiments of the present disclosure, the base station informs theUE which cells support the connection resume function through the systeminformation, and determines whether the MME supports the connectionresume function. The UE starts to perform the connection resumeprocedure after knowing that the cell supports the connection resumefunction. The base station transmits the context information activationrequest to the MME to inform the MME to activate the saved contextinformation, after making sure that the MME supports the connectionresume function. Therefore, the UE initiates the connection resumeprocedure at the cell supporting the connection resume procedure, andthe base station transmits the context information activation request tothe MME supporting the connection resume function, which may avoidfailure in the connection resume procedure.

In order to clarify the object, solutions and advantages of embodimentsof the present disclosure, embodiments of present disclosure will bedescribed clearly in detail in conjunction with accompanying drawings.

In an embodiment, a method for accessing a cell is provided. Referringto FIG. 1, the method is described in detail below.

First, a connection resume procedure is described briefly. In someembodiments, a UE saves context information, a base station saves thecontext information of the UE, and the MME saves the context informationof the UE as well.

The context information saved by the UE includes security algorithm(including security key), configuration parameters for a medium accesscontrol layer, configuration parameters for a physical layer,configuration parameters for a radio link control layer andconfiguration parameters for a non-access layer. The context informationof the UE saved by the base station mainly includes the configurationparameters for an access layer. The context information of the UE savedby the MME mainly includes the configuration parameters for thenon-access layer and information of a GTP tunnel corresponding to a dataradio bearer.

The UE accesses a cell administered by the base station and is in aconnected state to perform service interaction with the base station.When the base station determines to change the UE from the connectedstate to an idle state, the base station saves the context informationof the UE, and transmits an RRC connection suspend instruction and aresume identification to the UE. After receiving the RRC connectionsuspend instruction, the UE saves the context information configured bythe base station when it accesses the network and the resumeidentification. Besides, the base station transmits a contextinformation deactivation request to the MME to indicate the MME to savethe context information of the UE.

In this way, the UE, the base station and the MME save the contextinformation of the UE. After receiving the RRC connection suspendinstruction and the resume identification, the UE is no longer in theconnected state and enters a special idle state which is different froma common idle state. As the UE has saved the context information in thelast connected state, the UE can perform cell selection using anexisting cell selection and reselection mechanism or a strengthened cellselection and reselection mechanism in the special idle state. Inembodiments below, a strengthened cell reselection mechanism isdescribed, and both the special idle state and the common idle state arecalled an idle state.

In S101, system information is transmitted to a UE.

In some embodiments, when the UE is in an idle state, the UE may performcell selection or cell reselection during which process systeminformation may be received from a cell administered by a base station.The system information may include information indicating whether thecell supports a connection resume function. Therefore, based on thesystem information, the UE can know whether the cell transmitting thesystem information supports the connection resume function.

In some embodiments, a new cell may be added in the system informationwhen the cell transmits the system information. The new cell may be anindication information element which is used for indicating whether thecell supports the connection resume function.

In some embodiments, the indication information element may be a one-bitcell. When it is 1, it indicates that the cell supports the connectionresume function; and when it is 0, it indicates that the cell does notsupport the connection resume function.

In some embodiments, indication information elements may be set to havedifferent bits according to different PLMN identifications. A pluralityof indication information elements which have different bits maycorrespond to different PLMN identifications, respectively. In thissituation, the cell is shared by the network, and the system informationof the cell indicates a plurality of PLMN identifications.

For example, the PLMN identification for China Mobile is 46000, and thePLMN identification for China Unicom is 46001. The indicationinformation element corresponding to the PLMN identification for ChinaMobile is set to be one-bit, the indication information elementcorresponding to the PLMN identification for China Unicom is also set tobe one-bit, and the two indication information elements are located indifferent bits of the system information.

After accessing the cell administered by the base station, the UEacquires the indication information element which corresponds to a PLMNidentification the UE has registered to determine whether the currentlyaccessed cell supports the connection resume function. As the UEaccesses the network and establishes services successfully formerly, itindicates that the UE has registered in the network, and the UE canacquire the PLMN identification. For example, assume that the indicationinformation element corresponding to the PLMN identification for ChinaMobile being set to be 1 indicates that the connection resume functionis supported, and being other values indicates that the connectionresume function is not supported. When the PLMN identification the UEregistered is 46000, if a value of the indication information elementacquired by the UE is 1, the UE determines that the currently accessedcell supports the connection resume function.

Those skilled in the art can understand that, the different PLMNidentifications of a shared cell may employ indication informationelements with a same bit, which indicates that the different PLMNidentifications have the same connection resume function.

In practice, when system information blocks are to be read, the UEalways reads a system information block 1 (SIB1) first, and then readsother system information blocks (such as SIB2, SIB3 . . . ) followingthe system information block 1, successively.

If the indication information element is set in a particular systeminformation block rather than SIB1 in a cell system information, the UEneeds to read all the system information blocks before the particularsystem information block to know whether the cell supports theconnection resume function. However, if the indication informationelement is set in SIB1, the UE only needs to read SIB1 to know whetherthe cell supports the connection resume function. If knowing that thecell does not support the connection resume function based on SIB1, theUE does not need to read any other system information blocks, so thatpower consumption of the UE may be reduced.

In some embodiments, when the UE performs cell selection or cellreselection in the idle state, if only one frequency is detected to meeta cell reselection criterion, a cell having the maximum signal strengthvalue at the frequency is selected to camp on.

In some embodiments, when a plurality of frequencies meeting the cellreselection criterion are detected and each frequency has a cell havingthe maximum strength value measured by the UE, the UE can select onecell having the maximum strength value at each of the plurality offrequencies using existing measurement methods. The selected cell ateach frequency is the strongest cell among all the cells at thefrequency. Among the cells having the maximum strength value at theplurality of frequencies, the UE may select one cell supporting theconnection resume function to camp on. That is to say, if a plurality ofstrongest cells at different frequencies are detected and meet the cellreselection criterion, the UE preferentially selects a cell supportingthe connection resume function.

For example, there are three frequencies meeting the cell reselectioncriterion, including f1, f2 and f3. Cell 1, Cell 2 and Cell 3 are cellswhich have the maximum signal strength values at the frequencies f1, f2and f3, respectively. Among the three cells, Cell 1 has the maximumsignal strength value and does not support the connection resumefunction, Cell 2 has the second greatest signal strength value and doesnot support the connection resume function, Cell 3 has the minimumsignal strength value and supports the connection resume function, andall the three cells meet the cell reselection criterion (i.e., Scriterion in the standard TS36.304). In this situation, the UE mayselect Cell 3 at the frequency f3 to camp on.

In some embodiments, when a plurality of frequencies meeting the cellreselection criterion are detected, and at least two cells among thecells having the maximum strength values at the plurality of frequenciessupport the connection resume function, the UE may select one of the atleast two cells randomly, or select one cell having a highest frequencypriority among the at least two cells.

For example, there are three frequencies meeting the cell reselectioncriterion, including f1, f2 and f3. Cell 4, Cell 5 and Cell 6 are cellswhich have the maximum signal strength values at the frequencies f1, f2and f3, respectively. Among the three cells, Cell 4 has the maximumsignal strength value and does not support the connection resumefunction, Cell 5 has the second greatest signal strength value andsupports the connection resume function, Cell 6 has the minimum signalstrength value and supports the connection resume function, and all thethree cells meet the cell reselection criterion (i.e., S criterion inthe standard TS36.304). In this situation, the UE may select one of Cell5 and Cell 6 randomly or based on frequency priorities of thefrequencies f2 and f3 to camp on the selected cell.

In S102, after an RRC connection resume request is received from the UE,a resume identification of the UE is acquired from the RRC connectionresume request.

In some embodiments, when the UE has service demand with the basestation, the UE may initiate a random access procedure, during which anRRC connection resume request is transmitted to the base station. Insome embodiments, a resume identification of the UE which has been savedby the UE may be contained in the RRC connection resume request. Theresume identification of the UE was allocated by a base station whichthe UE accessed formerly.

When in the idle state, the UE may perform cell selection or cellreselection. After the cell selection or cell reselection, a basestation corresponding to the cell the UE accesses may be same as thatthe UE accessed formerly, or different from that.

For example, the context information the UE saves currently wasallocated by a first base station. After the cell selection or cellreselection, the base station corresponding to the cell the UE accessesis a second base station. The first base station and the second basestation may be the same one or different ones.

After the cell reselection, the cell the UE accesses may be still oneadministered by the first station. During the random access procedure,the RRC connection resume request may carry the resume identification ofthe UE. Therefore, the first station can acquire the resumeidentification of the UE from the RRC connection resume request.Afterwards, S103 is performed.

In S103, context information of the UE is looked up based on the resumeidentification, and an RRC connection resume acknowledgement message istransmitted to the UE after the context information is found.

In some embodiments, the base station looks up the saved contextinformation of the UE based on the resume identification, and transmitsthe RRC connection resume acknowledgement message to the UE after thecontext information is found. A connection resume procedure of an accesslayer is completed.

Afterwards, a connection resume procedure of a non-access layer is to beperformed, which includes S104 to S106.

In S104, after it is determined that an MME supports the connectionresume function, a context information activation request is transmittedto the MME.

In some embodiments, whether the MME supports the connection resumefunction is determined first. If the MME does not support the connectionresume function, S104 is not performed, and subsequent steps are alsonot performed. That is, the connection resume procedure may not beperformed successfully. If it is determined that the MME supports theconnection resume function, the base station transmits the contextinformation activation request to the MME. The context informationactivation request may include identification information of the UE, sothat the MME can know which terminal the UE that performs the connectionresume procedure is.

In some embodiments, the MME may transmit a message which includesinformation indicating that the MME supports the connection resumefunction to the base station. After receiving the message, the basestation can determine that the MME supports the connection resumefunction. On the contrary, if not receiving any message includinginformation indicating that the MME supports the connection resumefunction, the base station may determine that the MME does not supportthe connection resume function.

In some embodiments, during the setup of S1 interface by the basestation and the MME, the MME may inform the base station that the MMEsupports the connection resume function through an S1 interface setupresponse message, that is, containing the information indicating thatthe MME supports the connection resume function in the S1 interfacesetup response message.

In some embodiments, the MME may inform the base station that the MMEsupports the connection resume function through an MME configurationupdate message, that is, containing the information indicating that theMME supports the connection resume function in the MME configurationupdate message. In practice, within a time period, the MME may notsupport the connection resume function, but after an update of the MME,the updated MME may support the connection resume function. The updatedMME may transmit an MME configuration update message to the basestation, so that the base station knows that the updated MME supportsthe connection resume function.

In some embodiments, when the base station determines to change the UEfrom the connected state to the idle state, and saves the contextinformation of the UE, the base station transmits a context informationdeactivation message to the MME, to ask the MME to save the contextinformation of the UE. In this way, when the UE executes the resumeprocedure, the MME can reuse the context information of the UE. Afterreceiving the context information deactivation message, the MME feedsback to the base station a deactivation acknowledgement message ifsupporting the connection resume function, or a deactivation failuremessage which indicates that the MME doesn't support the connectionresume function if not supporting the connection resume function.Accordingly, the base station determines that the MME supports theconnection resume function if the deactivation acknowledgement messageis received, or determines that the MME doesn't support the connectionresume function if the deactivation failure message is received.

In S105, a context information activation acknowledgement message isreceived from the MME.

In some embodiments, as the MME supports the connection resume function,the MME has saved the context information of the UE. After receiving thecontext information activation request from the base station, the MMEacquires the identification information of the UE from the contextinformation activation request. Based on the identification informationof the UE, the MME looks up the context information of the UE which hasbeen saved. After finding the context information of the UE, the MME maytransmit the context information activation acknowledgement message tothe base station.

Reception of the context information activation acknowledgement messageby the base station may indicate that the connection resume procedure ofthe non-access layer is finished.

In S106, a notification message is transmitted to the UE, wherein thenotification message includes information indicating that a bearer isresumed.

After S101 to S105 are performed, the connection resume procedures ofthe access layer and the non-access layer are finished. A bearer betweenthe UE and the base station, and a bearer between the base station andthe MME are gotten through, and the UE can perform service interactionswith the base station. In this situation, the base station may transmita notification message to the UE, to inform the UE that the bearer isgotten through currently, that is, to transmit information indicatingthat the bearer is resumed.

In the existing techniques, a UE doesn't know whether a currentlyaccessed cell supports a connection resume function, and a base stationdoesn't know whether a connected MME supports the connection resumefunction as well. After cell selection or cell reselection, the UE caninitiate a connection resume procedure if it has saved the contextinformation. However, the currently accessed cell may not support theconnection resume function. Therefore, the connection resume procedureinitiated by the UE may fail. Accordingly, the base station may notexecute the connection resume procedure successfully as it doesn't knowwhether the connected MME supports the connection resume function.

In embodiments of the present disclosure, the base station informs theUE which cells support the connection resume function through the systeminformation, and determines whether the MME supports the connectionresume function. The UE starts to perform the connection resumeprocedure after knowing that the cell supports the connection resumefunction. The base station transmits the context information activationrequest to the MME to ask the MME to activate the saved contextinformation, after making sure that the MME supports the connectionresume function.

Therefore, it is ensured that the UE initiates the connection resumeprocedure at the cell supporting the connection resume procedure, andthe base station transmits the context information activation request tothe MME supporting the connection resume function, which may avoidfailure in the connection resume procedure.

Referring to FIG. 2, a base station 20 is provided in an embodiment,including a first transmitting unit 201, an acquiring unit 202, alooking up unit 203, a second transmitting unit 204, a determining unit205, a third transmitting unit 206, a receiving unit 207 and a fourthtransmitting unit 208.

The first transmitting unit 201 may be configured to transmit systeminformation to a UE, wherein the system information includes informationindicating whether the cell supports a connection resume function.

The acquiring unit 202 may be configured to acquire a resumeidentification of the UE from an RRC connection resume received from theUE.

The looking up unit 203 may be configured to look up context informationof the UE based on the resume identification.

The second transmitting unit 204 may be configured to transmit an RRCconnection resume acknowledgement message to the UE after the contextinformation is found by the looking up unit 203.

The determining unit 205 may be configured to determine that an MMEsupports the connection resume function.

The third transmitting unit 206 may be configured to transmit a contextinformation activation request to the MME, wherein the contextinformation activation request includes identification information ofthe UE.

The receiving unit 207 may be configured to receive a contextinformation activation acknowledgement message from the MME, wherein thecontext information activation acknowledgement message is transmittedafter the MME finds the context information of the UE according to theidentification information of the UE.

The fourth transmitting unit 208 may be configured to transmit anotification message to the UE, wherein the notification messageincludes information indicating that a bearer is resumed.

From above, the base station informs the UE which cells support theconnection resume function through the system information, anddetermines whether the MME supports the connection resume function. TheUE starts to perform the connection resume procedure after knowing thatthe cell supports the connection resume function. The base stationtransmits the context information activation request to the MME toinform the MME to activate the saved context information, after makingsure that the MME supports the connection resume function. Therefore,the UE initiates the connection resume procedure at the cell supportingthe connection resume procedure, and the base station transmits thecontext information activation request to the MME supporting theconnection resume function, which may avoid failure in the connectionresume procedure.

In some embodiments, the determining unit 205 may be configured todetermine that a message which includes information indicating that theMME supports the connection resume function is received from the MME.

In some embodiments, the message which includes information indicatingthat the MME supports the connection resume function may be one of thefollowing messages: S1 interface setup response message; an MMEconfiguration update message; and a deactivation acknowledgement messagefed back by the MME, wherein the deactivation acknowledgement message isgenerated after the MME receives a deactivation message.

In some embodiments, when the UE which has saved the resumeidentification performs cell reselection, if a plurality of cells aredetected to have maximum signal strength values at different frequenciesand meet a cell reselection criterion, a cell selected by the UE is thecell supporting the connection resume function.

Those skilled in the art can understand that all of or a portion of theprocesses in the method provided in the above embodiments can beimplemented by related hardware with instruction of computer program.The computer program may be stored in a readable storage medium, andinclude the processes of the method provided in the above embodimentswhen it is executed. The readable storage medium may be a magnetic disk,an optical disk, a Read-Only Memory (ROM) or a Random Access Memory(RAM).

Although the present disclosure has been disclosed above with referenceto preferred embodiments thereof, it should be understood that thedisclosure is presented by way of example only, and not limitation.Those skilled in the art can modify and vary the embodiments withoutdeparting from the spirit and scope of the present disclosure.

What is claimed is:
 1. A method for accessing a cell, comprising:transmitting system information to a User Equipment (UE), wherein thesystem information comprises information indicating whether the cellsupports a connection resume function; after receiving a Radio ResourceControl (RRC) connection resume request from the UE, acquiring a resumeidentification of the UE from the RRC connection resume request; lookingup context information of the UE based on the resume identification, andtransmitting an RRC connection resume acknowledgement message to the UEafter the context information is found; after determining that aMobility Management Entity (MME) supports the connection resumefunction, transmitting a context information activation request to theMME, wherein the context information activation request comprisesidentification information of the UE; receiving a context informationactivation acknowledgement message from the MME, wherein the contextinformation activation acknowledgement message is transmitted after theMME finds the context information of the UE according to theidentification information of the UE; and transmitting a notificationmessage to the UE, wherein the notification message comprisesinformation indicating that a bearer is resumed.
 2. The method accordingto claim 1, wherein determining that an MME supports the connectionresume function comprises: determining that a message which comprisesinformation indicating that the MME supports the connection resumefunction is received from the MME.
 3. The method according to claim 2,wherein the message which comprises information indicating that the MMEsupports the connection resume function is one of the followingmessages: S1 interface setup response message; an MME configurationupdate message; and a deactivation acknowledgement message fed back bythe MME, wherein the deactivation acknowledgement message is generatedafter the MME receives a deactivation message.
 4. The method accordingto claim 1, wherein the system information comprises an indicationinformation element which is used for indicating whether the cellsupports the connection resume function.
 5. The method according toclaim 4, wherein the indication information element is set in a systeminformation block
 1. 6. The method according to claim 4, wherein thereare a plurality of indication information elements which correspond todifferent Public Land Mobile Network (PLMN) identifications,respectively.
 7. The method according to claim 5, wherein there are aplurality of indication information elements which correspond todifferent Public Land Mobile Network (PLMN) identifications,respectively.
 8. The method according to claim 1, wherein when the UEwhich has saved the resume identification performs cell reselection, ifa plurality of cells are detected to have maximum signal strength valuesat different frequencies and meet a cell reselection criterion, a cellselected by the UE is the cell supporting the connection resumefunction.
 9. A base station, comprising: a first transmitting unit,configured to transmit system information to a User Equipment (UE),wherein the system information comprises information indicating whetherthe cell supports a connection resume function; an acquiring unit,configured to acquire a resume identification of the UE from an RadioResource Control (RRC) connection resume received from the UE; a lookingup unit, configured to look up context information of the UE based onthe resume identification; a second transmitting unit, configured totransmit an RRC connection resume acknowledgement message to the UEafter the context information is found by the looking up unit; adetermining unit, configured to determine that an Mobility ManagementEntity (MME) supports the connection resume function; a thirdtransmitting unit, configured to transmit a context informationactivation request to the MME, wherein the context informationactivation request comprises identification information of the UE; areceiving unit, configured to receive a context information activationacknowledgement message from the MME, wherein the context informationactivation acknowledgement message is transmitted after the MME findsthe context information of the UE according to the identificationinformation of the UE; and a fourth transmitting unit, configured totransmit a notification message to the UE, wherein the notificationmessage comprises information indicating that a bearer is resumed. 10.The base station according to claim 9, wherein the determining unit isconfigured to determine that a message which comprises informationindicating that the MME supports the connection resume function isreceived from the MME.
 11. The base station according to claim 10,wherein the message which comprises information indicating that the MMEsupports the connection resume function is one of the followingmessages: S1 interface setup response message; an MME configurationupdate message; and a deactivation acknowledgement message fed back bythe MME, wherein the deactivation acknowledgement message is generatedafter the MME receives a deactivation message.